Endoscopic surgical procedures are routinely performed in order to accomplish various surgical tasks. In such a surgical procedure, small incisions or portals are made in the patient. An endoscope, which is a device that allows medical personnel to view the surgical site, is inserted in one of the portals. Surgical instruments used to perform other tasks are inserted into other portals. The surgeon views the surgical site through the endoscope to determine how to manipulate the surgical instruments in order to accomplish the desired procedure. An advantage of performing endoscopic surgery is that, since the portions of the body that are cut open are minimized, the portions of the body that need to heal after the surgery are likewise reduced. Moreover, during an endoscopic surgical procedure, only relatively small portions of the patient's internal organs and tissue are exposed to the open environment. This minimal opening of the patient's body lessens the extent to which the organs and tissue are open to infection.
The ability to perform endoscopic surgery is enhanced by the development of powered surgical tools especially designed to perform such procedures. Once such tool is sold by the assignee hereof under the trademark FORMULA®. This tool is in the form of a cylindrical handpiece designed to be held in the hand of the surgeon. The handpiece has a front or distal end provided with a coupling assembly for releasably holding a cutting accessory, and a motor disposed within a handpiece housing which drives the accessory. The cutting accessories, such as shavers, drills and burs, include an outer housing element having a hub appropriately configured to cooperate with the coupling assembly of the handpiece to lock the accessory thereto and an elongated housing tube having a proximal end fixed to the hub, and an inner cutting element having a drive shaft disposed within the housing tube. When the accessory is attached to the handpiece, the handpiece motor couples to the drive shaft of the accessory and moves same relative to the housing tube. The handpiece motor is selectively actuable to drive the accessory drive shaft so as to cause a desired cutting action at the distal end of the accessory. The handpiece is associated with a control unit which controls the functioning thereof, and is actuated by the user via appropriate buttons provided on the handpiece itself, at the control unit or through use of a footswitch.
In an endoscopic surgical procedure, irrigating fluid is introduced into the surgical site. This fluid serves as a transport media for removing tissue and debris from the surgical site. In order to remove the irrigating fluid and the material contained therein, the above handpiece and the various accessories which are usable therewith together define a suction conduit. A suction pump is connected to the handpiece to provide the suction force needed for drawing the fluid and material away from the surgical site. In order to control the suction flow through the accessory and the handpiece, the handpiece is typically provided with a manually operated valve which is manipulated by the surgeon to control suction of material away from the surgical site.
Mechanical cutting accessories, such as the shaver, drill and bur discussed above, are commonly used in arthroscopic procedures, and allow for the resection of hard and soft bodily tissues, for example, those found within the knee, shoulder and other joints. A bur-type cutting accessory is sometimes used to resect bone or other hard tissues, and includes a cutting head with cutting features which when rotated serve to cut away targeted bone or hard tissue. Such cutting features may include straight or helically-oriented cutting edges which extend longitudinally along the cutting head of the bur. Another bur-type cutting accessory is a diamond bur which includes diamond particles as cutting features which are embedded in a metal surface of the cutting head. Such bur-type cutting accessories often have solid cutting heads so as to have sufficient strength for abrading or cutting hard tissue. A bur-type cutting accessory includes a cutting head with cutting features such as those described above which are exposed through a window formed at the distal end of the outer housing element when the cutting element is located therein. In some bur-type cutting accessories, the window formed in the outer housing element opens primarily sidewardly, so that the distal end of the outer housing element covers a portion or one side of the cutting features of the cutting head of the bur to allow the user to better target bone or hard tissue, and this type of configuration is sometimes referred to as a “hooded” bur. Alternatively, the entire geometry of the cutting head which defines the cutting features may project distally beyond the terminal end of the outer housing element, and this type of arrangement is often called “unhooded”. In a bur-type cutting accessory, as contrasted with a surgical shaver, the distal end of the outer housing element typically does not perform any tissue-cutting function, and serves essentially only to house and support the drive shaft of the inner cutting element and to shroud part of the cutting head thereof (in the case of a hooded arrangement), and the cutting of hard tissue is carried out by the cutting features of the cutting head. In an unhooded bur configuration, the outer housing element serves essentially only to house and support the drive shaft. As discussed above, bur-type cutting accessories are typically used for removal of particular bone or hard tissue types, and a variety of different bur geometries are available to specifically address the type of cutting the accessory is to carry out.
Further, in one conventional bur-type cutting accessory, the cutting element includes an elongate and hollow tubular drive shaft and a cutting head with cutting features is provided as a solid member which is fixedly mounted to the distal end of the drive shaft. In order to draw suction through the cutting element in this type of accessory, a suction opening is provided at the distal end of the drive shaft. The suction opening opens sidewardly outwardly and communicates with the hollow interior of the drive shaft, and is located proximally of the cutting features of the cutting head. In operation, bone or other hard tissue removed or cut away by the cutting head is suctioned into the hollow interior of the drive shaft through the window of the outer housing element and the suction opening. In this type of cutting accessory, it is possible that soft tissue can become wrapped around the cutting head in an area just proximal to the cutting features, which can block suction through the suction opening, prevent evacuation of surgical debris, and result in the surgeon's field of view becoming occluded. Such an occurrence will typically require that the surgeon disassemble the cutting accessory and manually unclog the suction opening of the accessory before continuing with the surgery.
Additionally, the various types of surgical cutting accessories as discussed above typically require some type of bearing arrangement which supports the inner cutting element as same rotates within the outer housing element. Such bearing arrangements may include one or more bushings or bearing sleeves provided on the inner cutting element which serve to radially support the inner cutting element within the outer housing element, and a thrust washer or spacer provided at the interface between the mating proximal portions of the inner cutting element and outer housing element which serves to axially support the inner cutting element relative to the outer housing element. In some devices, the bearing sleeve which provides radial support is a heat-shrunk plastic sleeve applied to the exterior of the drive shaft of the inner cutting element. The bushings/bearing sleeves are typically provided as separate components of the accessory, which can complicate assembly/manufacturing. Further, heat-shrunk plastic sleeves have a wide tolerance range, which can make it difficult to maintain the desired gap between relatively movable components.
In an effort to obviate or at least minimize the disadvantages of known surgical accessories, a suction arrangement is provided which can be utilized to both evacuate surgical debris from the surgical site and to provide a self-cleaning function for the cutting accessory. Further, a bearing arrangement provides both radial and axial support for the inner cutting element relative to the outer housing element. The bearing arrangement according to one embodiment is integrated into existing structures of the surgical cutting accessory, and thus provides a simpler and more cost-effective design.
Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. The words “forwardly” and “distally” will refer to the direction toward the end of the arrangement which is closest to the patient or which is first inserted into the patient, and the words “rearwardly” and “proximally” will refer to the direction toward the end of the arrangement which is furthest from the patient. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.